See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

**Understanding Rancid Butter and Butyric Acid** **Step 1: Define rancidity** Rancidity is the process of fat oxidation and decomposition, occurring when fats/oils are exposed to air, moisture, or microorganisms over time. **Step 2: Identify the source compound** Butter contains triglycerides (fats) with various fatty acid chains. The primary fatty acid in butter is **butyric acid** ($C_3H_7COOH$), which comprises about 3-4% of butter's composition. **Step 3: Understand rancid butter formation** When butter becomes rancid: $$\text{Triglycerides (with butyric acid)} \rightarrow \text{Free butyric acid} + \text{Glycerol}$$ Hydrolysis and oxidation release free fatty acids, particularly butyric acid, which has a characteristic foul, unpleasant smell—the distinctive odor of rancid butter. **Step 4: Eliminate other options** - **(A) Pyruvic acid**: Product of glucose metabolism, not present in butter - **(B) Lactic acid**: Produced by lactic acid bacteria, not a decomposition product of butter fats - **(D) Acetic acid**: Minor component; butyric acid is the primary volatile acid causing rancidity **Answer: (C) Butyric acid** — the main fatty acid released during butter rancidity, responsible for its characteristic pungent odor.